According to Steve Huey, who reviewed the album on behalf of the online music database AllMusic, "Sabbath's genius was finding the hidden malevolence in the blues, and then bludgeoning the listener over the head with it. ... The standard pentatonic blues scale always added the tritone, or flatted fifth, as the so-called 'blues note;' Sabbath simply extracted it and came up with one of the simplest yet most definitive heavy metal riffs of all time. ...

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• Approx Pages: 5
• Has Bibliography
• Grade Level: Undergraduate